Group or point-to-multipoint communication systems have been used to provide communications generally between a central location and one or more users of the system. For example, dispatch systems using Land Mobile Radios (LMRs) have been used in trucks, taxis, buses, and other vehicles in order to communicate scheduling information between a central dispatch center and one or more corresponding fleet vehicles. Communications may be directed at a specific vehicle in the fleet or to all vehicles simultaneously.
Another example of a point to multipoint communications system is a wireless push-to-talk system. Such a system allows a group of individuals, each having a wireless communication device, to communicate with other members of the group. Typically, a push-to-talk system relies on a single frequency, or dedicated channel, over which communications are received by the wireless communication devices. In most systems, only one member may transmit information to the other members at any given time. However, all members can listen to the dedicated broadcast channel to receive communications from the single member who is transmitting. Members desiring to transmit to other members of the system typically send an access request by depressing a push-to-talk (“PTT”) button on their respective communication device that allows the user sole access to the dedicated channel. Pushing the button indicates the user's request for the “floor.” If granted the floor, or talker permission, the user then generally speaks for a few seconds, after which the user releases the PTT button, and other speakers can request the floor. Communication is generally from one speaker to a group of listeners, but may be one-to-one. As mentioned above, this service has traditionally been used in applications where one person, a “dispatcher,” needs to communicate to a group of people, such as field service personnel or taxi drivers. The group of people requiring communications with each other is commonly known as a “net,” and each member of the net may be referred to as a “net member.”
Similar services have been offered on the Internet and are generally known as “voice chat.” These services are usually implemented as personal computer applications that send vocoder frames in Internet protocol (IP) packets, i.e., voice-over-IP (VoIP) service, to a central group chat server, or possibly from client-to-client in a peer-to-peer service.
In some instances, these group communications systems can be wasteful because they are over-inclusive. For example, in the case of public safety and/or emergency response, a dispatcher typically utilizes a broadcast communication to notify a particular service group, or group of net members, when an event occurs. For example, all police receive a broadcast communication that a particular crime is in progress at a particular location. Generally, only one or a select number of net members will actually end up responding to the broadcast, based on any number of factors such as their availability, their proximity to the crime location, their capability of dealing with the particular crime, etc. As such, the net is generally over-inclusive. With such an over-inclusive net, resources are wasted. Such resources include the dedicated broadcast channel on all but those select net members who are able to respond to the communication, the time spent by each net member associated with listening and responding to the broadcast, etc. Thus, a group communications system is desired which provides for a more efficient use of the resources associated with the group communications system.